Parenting Advice...seeking your help!

So this blog I am actually reaching out to all of you moms out there and hoping that you will be able to offer some advice.

I have identical twin girls that are 6 1/2 years old.  They are such good girls and we are so proud of them.  Recently, I have noticed that any time they are given "free range" where they are not being watched like a hawk, they seem to be making bad decisions.  They do the things that they have been asked NOT to do over and over again.  When asked why they decided to do that, they will say..."well mom, we really wanted to.  We didn't want to listen to what you said."  I appreciate the honesty, but how am I ever supposed to be able to trust them to do the right things when given the opportunity.

For example, yesterday my husband washed my car and it was sparkling clean.  This morning the girls wanted to go down in the garage and play with our kitties.  We didn't see any reason why they couldn't.  Is there stuff down there that they shouldn't play with, of course, but we trusted them to stay away from it.

I just got in my car to run to the store and noticed that there were finger prints all over my driver side window...a little odd considering the car was just washed.  Coming back from the store with the headlights shining in my windshield, I noticed that I have a TON of little hands all over my window...THEY WERE ON TOP OF MY CAR!! 

I am totally blown away.  I was given a lot of freedom at their age and can honestly say that I NEVER climbed on my mom and dads car. 

So I am going out on a limb here and asking for help.  Please, please leave a comment on what you think we should or should not do.  Things that have worked or have not worked for you.  Sometimes, it better to learn by others mistakes than their successes...so anything you have to add is greatly appreciated!

From one mom to another, I thank you in advance for your help!